The final scene of chapter one is bleak. We find ourselves in the middle of the woods, most of the trees bare as winter sets in. There's snow on the ground (even though this is Atlanta). There are only three characters on the page, and one of them is dead. Shane lies face down on the ground in a pool of his own blood, his rifle by his side. Rick consoles Carl, who just shot Shane with the pistol that lies on the ground nearby. Carl cries, and says, "It's not the same as killing the dead ones, daddy" (760).
In a horror story, killing the bad guys comes with a certain kind of fun thrill. Blowing away the undead has a visceral feeling not unlike that of playing a video game. It's not like they're human anymore, right? But when Carl kills Shane, a human, it's not all fun and games anymore. The Walking Dead just got real, y'all.
In a serialized book, the last scenes always set us up for the next chapters. That's definitely the case here. How will the campers react when they find out that Rick's gun-toting son killed one of their own? Where will Rick, Carl, and Lori go if they get kicked out of the group? Until we find out, Rick has to do his best to comfort his son in a world where he no longer has any control.